There is a polarization plane detection device configured to separate a radio wave such as a linearly polarized wave received by a dual right-hand/left-hand circularly polarized antenna into a right-hand circularly polarized wave signal and a left-hand circularly polarized wave signal and obtain a polarization plane of the received radio wave from the separated right-hand circularly polarized wave signal and left-hand circularly polarized wave signal. This device alternately switches and outputs the separated right-hand circularly polarized wave signal and left-hand circularly polarized wave signal at a sufficiently high speed, and shapes the output right-hand circularly polarized wave signal and left-hand circularly polarized wave signal using a low pass filter. By detecting a phase difference between the shaped right-hand circularly polarized wave signal and left-hand circularly polarized wave signal, the polarization plane detection device obtains the polarization plane of the received radio wave.
This device uses all the separated right-hand circularly polarized wave signal and left-hand circularly polarized wave signal to detect the polarization plane, and so it is not possible to use the dual right-hand/left-hand circularly polarized antenna for communication or the like. Furthermore, since output destinations of the right-hand circularly polarized wave signal and the left-hand circularly polarized wave signal need to be switched at a high frequency, there are problems that a switching circuit becomes complicated or noise is produced.